Xenobiotic-Metabolizing Enzymes

我们已经产生了几种P450的人源化小鼠，这些P450对药物和致癌物质代谢至关重要。这些包括表达CYP 1A 1、CYP 1A 2、CYP 2D 6、CYP 2 E1、CYP 3A 4和CYP 3A 7的小鼠。CYP3A4。CYP 3A 4负责市场上约50%药物的代谢，因此参与了大量临床相关的药物间相互作用，当两种药物同时给药时，这两种药物都是CYP 3A 4底物。生成了一种在肠道中表达人CYP 3A 4的CYP 3A 4小鼠模型（命名为hCYP 3A 4），并证明其表达CYP 3A 4蛋白并进行咪达唑仑1 '-羟基化和4-羟基化;这些活性几乎完全被抗CYP 3A 4单克隆抗体抑制（注-该论文被授予2003年药物代谢和处置年度论文）。当药物经口给药时，咪达唑仑的药代动力学与野生型小鼠相比发生了改变;静脉给药未显示药物消除差异，因此证明了肠道中CYP 3A 4表达对经口给药药物药代动力学的重要性。酮康唑是一种已知的CYP 3A 4抑制剂，可增加口服咪达唑仑的最大血药浓度。这些结果表明，hCYP 3A 4小鼠将是一个合适的体内动物模型，用于评估候选药物的人肠道CYP 3A 4代谢以及潜在的食品-药物和药物-药物相互作用在临床前药物开发中。hCYP 3A 4雌性小鼠泌乳不足，导致幼仔存活率低。(Note- 本文中的一幅图被授予内分泌学的封面图片）。hCYP 3A 4泌乳小鼠的乳腺明显发育不全，乳汁含量低。泌乳受损表型与hCYP 3A 4小鼠血清雌二醇水平显著降低相关。这些结果表明，CYP 3A 4可能在雌二醇稳态中发挥重要作用，并建议在使用可能增加雌二醇代谢和消除的CYP 3A 4诱导剂治疗妊娠或哺乳期妇女时应谨慎。在含有CYP 3A 4和CYP 3A 7的第二系小鼠中检查CYP 3A 4转基因的调节，命名为hCYP 3A 4/CYP 3A 7。一项时间进程研究显示，CYP 3A 4蛋白和RNA在未成熟雄性小鼠的肝脏中表达，当小鼠在6周龄达到成熟时，检测不到。相反，CYP 3A 4在未成熟和成年雌性动物中均表达，这一研究让人想起大鼠中P450的性别依赖性调节。在hCYP 3A 4/CYP 3A 7小鼠的雄性和雌性肝脏中，组成型雄甾烷受体（CAR）激活剂苯巴比妥也显著升高CYP 3A 4，证明了该小鼠模型中CYP 3A 4转基因的药物诱导。此外，在hCYP 3A 4/CYP 3A 7雄性小鼠中连续输注重组生长激素（GH）（其覆盖雄性中的低水平脉动雄性血浆GH特征），使肝脏CYP 3A 4 mRNA和蛋白质增加至正常雌性水平。连续GH处理也使内源性小鼠Cyp 2b和Cyp 3a 44基因的表达雌性化。这些数据表明，人CYP 3A 4含有对发育表达和性二型性的内源性激素调节剂（特别是GH）产生反应所需的所有顺式元件。还揭示了GH在确定人类肝脏中CYP 3A 4的性别依赖性表达中的潜在作用。这些发现与人类研究一致，显示肝脏中CYP 3A 4蛋白和mRNA的表达具有性别依赖性。此外，这些研究表明，GH治疗可能会改变CYP 3A 4底物的药代动力学和药效学特性，导致药物在人体内的代谢和处置增强。

We have generated humanized mice for several P450s that are critical for drug and carcinogen metabolism. These include mice expressing CYP1A1, CYP1A2, CYP2D6, CYP2E1, CYP3A4 and CYP3A7. CYP3A4. CYP3A4 is responsible for the metabolism of approximately 50% of drugs on the market and thus is involved in a large number of clinically relevant drug-drug interactions that occur when two drugs are co-administered that are both CYP3A4 substrates. A CYP3A4 mouse model that expresses human CYP3A4 in the intestine, designated hCYP3A4, was generated and demonstrated to express the CYP3A4 protein and to carry out midazolam 1'-hydroxylation and 4-hydroxylation; these activities were almost completely inhibited by an anti-CYP3A4 monoclonal antibody (Note - This paper was awarded the 2003 Paper of the Year in Drug Metabolism and Disposition). Midazolam pharmacokinetics were altered as compared to wild-type mice when the drug was orally administered; intravenous administration did not reveal a differences in drug elimination thus demonstrating the importance of expression of CYP3A4 in gut on the pharmacokinetics of orally administered drugs. Ketoconazole, a known inhibitor of CYP3A4, increased maximum plasma concentration orally dosed midazolam. These results suggest that the hCYP3A4 mouse would be an appropriate in vivo animal model for the evaluation of human intestine CYP3A4 metabolism of drug candidates and potential food-drug and drug-drug interactions in preclinical drug development.The hCYP3A4 mice displayed a remarkable phenotype that yields clues into the physiological function of this P450. hCYP3A4 female mice were deficient in lactation resulting in low pup survival. (Note - A figure from this paper was awarded the cover picture in Endocrinology). The mammary glands of hCYP3A4 lactating mice were markedly underdeveloped and had low milk content. The impaired lactation phenotype was associated with significantly reduced serum estradiol levels in hCYP3A4 mice. These results suggest that CYP3A4 may play an important role in estradiol homeostasis and suggest caution when treating pregnant or lactating women with CYP3A4 inducers that may increase estradiol metabolism and elimination.Regulation of the CYP3A4 transgene was examined in a second line of mice containing both CYP3A4 and CYP3A7, designated hCYP3A4/CYP3A7. A time course study revealed that CYP3A4 protein and RNA were expressed in the liver of immature male mice and became undetectable when the mice reached maturity at 6 weeks of age. In contrast, CYP3A4 was expressed in both immature and adult females studies were reminiscent of the gender-dependent regulation of P450s in rat. CYP3A4 was also markedly elevated by the constitutive androstane receptor (CAR)-activator phenobarbital in both male and female livers of hCYP3A4/CYP3A7 mice, demonstrating drug induction of the CYP3A4 transgene in this mouse model. Furthermore, continuous infusion of recombinant growth hormone (GH) in hCYP3A4/CYP3A7 male mice, which overrides the low-level pulsatile male plasma GH profile in males, increased hepatic CYP3A4 mRNA and protein to normal female levels. Continuous GH treatment also feminized the expression of endogenous murine Cyp2b and Cyp3a44 genes. These data demonstrated that human CYP3A4 contains all of the cis elements required for it to respond to endogenous hormonal regulators of developmental expression and sexual dimorphism, in particular GH. A potential role for GH in determining the sex-dependent expression of CYP3A4 in human liver was also revealed. These finding are in agreement with studies in humans showing a gender dependent expression of CYP3A4 protein and mRNA in liver. Further, these studies suggest that GH therapy may alter the pharmacokinetic and pharmacodynamic properties of CYP3A4 substrates, leading to enhanced metabolism and disposition of drugs in humans.CYP2E1.